Machinists have been grappling with the problems of securely clamping and holding workpieces in order to carry out desired machining operations for as long as machine shops have been in existence. Due to the wide variety in sizes and shapes of workpieces, and the wide range of machining operations to be performed on them, machinists are continuously challenged to come up with the right workpiece holder for many unusual or specialized jobs. The venerable V-block emerged early on as the best multipurpose device in this regard, and has served thereafter as the baseline workpiece holder from which a wide range of variants have evolved. No matter what type of workpiece is involved--rectangular, cylindrical, curved castings, or other odd shapes big or small--and regardless of what type of machining operation is to be performed--grinding, drilling, cutting, milling, and so forth--there is most likely some form of V-block that will properly retain the workpiece while the operation is being completed.
Descriptions of typical prior art devices for clamping and holding workpieces during machining operations are found in a number of U.S. patents.
U.S. Pat. No. 1,372,661 to Secord discloses an early (1921) workpiece holding appliance having three separately adjustable jaws, each of which may be individually adjusted in both rotation and traverse.
U.S. Pat. No. 4,340,211 to Chiappetti discloses a V-block clamp having individually adjustable jaws that are directed mainly to holding items having curved outer surfaces, such as cylindrical workpieces. A cylindrical workpiece retained in the clamp disclosed would experience combined up/down as well as left/right movement in response to an adjustment of either jaw.
U.S. Pat. No. 4,583,432 to Bricker discloses a method of centering an article relative to a concentrically rotatable cylinder which includes a slightably adjustable centering member as part of a more or less conventional V-block device.
Additional teachings of various types of prior art workpiece holders are found in U.S. Pat. No. 3,887,202 to Zapart, U.S. Pat. No. 3,094,821 to Eckert and U.S. Pat. No. 1,349,963 to Jerrim.
Despite the generous number of devices and techniques taught in the prior art, it is not uncommon for a tool maker to have to make up special jigs for a particular unusual part or machining task. However, these one time "fixes" are time consuming, often requiring auxiliary elements such as shims, spacers, and the like, and rarely lend themselves to a high degree of precision repeatability for follow on finished articles. Additionally, most V-block based workpiece holders favor carrying out machining operations (especially grinding) at locations on the workpiece which are symmetrical with respect to the outer dimensions of the workpiece. Indeed, to machine or grind a radius or diameter on a workpiece with the center line not symmetrical with its outside surfaces has been declared by many great toolmakers to be one of the most difficult tasks to do or to teach. Even when this particular task is actually accomplished, the repeatability of the process for multiple workpieces remains difficult to achieve. It is precisely this set of needs that the present adjustable jaw workpiece holder meets, thereby satisfying a long standing need for a simple V-block based workpiece holder having a V-point that is rapidly and precisely adjustable along both X and Y axes.